All I've ever seen, were Cast Iron.

 

 

They make excellent Decoy Anchors, ... otherwise, they tend to be low grade Cast, ... so basically, ... not much use for anything.

 

 

 

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Once you have enough, you could start a sash weight museum.  :D

iv seen people here reference wrought iron sash weights, so if thats the case forge it into whatever your imagination takes you to. dont try to forge them if they are cast though....

If you have enough, use them to weight something down.  If not needed for that, collect as many as you can find, and scrap them for dollars.  Use the dollars to buy something needed and useful.

The ones from my house (circa 1862) were 1 1/2" square wrought iron 16 to 18" long.  The only wrought ones I've ever seen thou, 99% of sash weights are low grade cast iron.  

The rounded end can be a vise-held sheet metal stake.

 

Sayings and Cornpone

"One man's mud is another man's adobe."

     Former New Mexico governor, Dave Cargo

I'd read that he square ones were wrought, but years of perusing the sash weight pile at my local building material recycler have not produced a single square sided one.  I've got a sash weight linked to a roller chain that lays across my anvil as a hold down.